Epoxy resin compositions containing aromatic disulfonamide salts

ABSTRACT

Latent curing epoxy resin compositions are described which comprise (1) an epoxy resin such as the diglycidyl ether of bisphenol A, (2) an aromatic disulfonamide such as diphenyl oxide disulfonamide and (3) a salt of an aromatic disulfonamide with substituted tertiary amines or hydrocarbon substituted phosphines wherein components (1), (2) and (3) are present in quantities so as to provide an amine hydrogen equivalent: epoxy equivalent ratio of at least about 0.9:1 and (3) is present in an amount greater than 1.0 weight percent based on the amont of (2).

United States Patent Smith [75] Inventor: Harry A. Smith, Midland, Mich.

[ 73] Assignee: The Dow Chemical Company,

Midland, Mich.

[22] Filed: Apr. 2, 1973 [21] Appl. No.: 347,171

[52] US. Cl. 260/47 EN, 117/132 BE, 117/161 ZB, 161/104, 260/2 N, 260/33.2 EP, 260/33.6 EP, 260/49, 260/59, 260/78.4 EP [51] Int. Cl C08g 30/14 [58] Field of Search.. 260/47 EN, 2 N, 59, 78.4 EP, 260/49, 79, 556 AR, 33.2 EP

{56] References Cited UNITED STATES PATENTS 2,712,001 6/1955 Greenlee 260/47 June 25, 1974 3,277,050 10/1966 Pettigrew ..260/47 Primary Examiner-William H. Short Assistant EraminerT. Pertilla Attorney, Agent, or FirmBenjamin G. Colley [5 7 ABSTRACT Latent curing epoxy resin compositions are described which comprise (1) an epoxy resin such as the diglycidyl ether of bisphenol A, (2) an aromatic disulfonamide such as diphenyl oxide disulfonamide and (3) a salt of an aromatic disulfonamide with substituted tertiary amines or hydrocarbon substituted phosphines wherein components (1), (2) and (3) are present in quantities so as to provide an amine hydrogen equivalent: epoxy equivalent ratio of at least about 09:1 and 3) is present in an amount greater than 1.0 weight percent based on the amont of (2).

8 Claims, N0 Drawings EPOXY RESIN COMPOSITIONS CONTAINING wherein each A is independently selected from the AROMATXC DISULFONAMIDE SALTS group consisting of a divalent hydrocarbon group having from 1 to 4 carbon atoms, S, SS,

BACKGROUND OF THE INVENTION This invention relates to latent curing epoxy resin 5 0 compositions comprising an epoxy resin and a salt of an g g ll. aromatic disulfonamide with substituted tertiary g amines or substituted phosphines.

Commonly employed latent curing agents for epoxy resins include accelerated dicyandiamide. It is also '10 X is hydrogen or a halogen and n is an integer known that aromatic disulfonamides are latent curing having an average Value f f about 0 to about agents for epoxy resins.

B. o o

O-CH C- CHg pom-( 0m )-cH,-c--cm on on, Q 1 [X X1 JD X X1 SUMMARY OF THE INVENTION wherein X and X; are independently selected from the It has now been discovered that epoxy resins employgroup consisting of hydrogen, an alkyl group having ing a salt of an aromatic polysulfonamide with substifrom about I to 4 carbon atoms and a halogen and n tuted tertiary amines or substituted phosphines as the is an integer having an average value of from about'0.l latent curing agent have greater latency than accelerto about 4;

ated dicyandiamide systems due to the tying up of the wherein R, R and R are independently hydrogen, an accelerator in the form of an inactive salt which can be alkyl or haloalkyl group having from about I to about reactivated by heat during the curing process. 4 carbon atoms, and a, b and c are integers, the sum of The latent curingepoxy resin compositions of the which is an integer having an average value of from present invention comprise about 3 to about 40;

1. an epoxy resin having an average of more than one 40 1,2-epoxy group per molecule, 2. an aromatic disulfonamide, and CH2 Q. \CH,

3. a salt of an aromatic disulfonamide with substituted tertiary amines or hydrocarbon substituted phosphines x wherein components (1), (2) and (3) are present in quantities so as to provide an amine hydrogen equiva- X lent: epoxy equivalent ratio of at least about 0.921 and is Presentln an amount greater than Weight P wherein X and X are as indicated in formula B cent based on the amount of (2). above DETAILED DESCRIPTION E X Suitable epoxy resins for use in this invention have an 0 lH: average of more than one 1,2-epoxy group per mole- CH2 -0 CH2 C. \CH2 cule. These include, for example, those epoxy resins represented by the following general formulae:

3 4 wherein X and X are independently selected from hy- S-S,' or a single bond, each R is independently hydrogen, chlorine and bromine. drogen, an aliphatic hydrocarbon group having from 1 im-zlfiom R 1 R1 o 0 (16,. F n our m-(j 1u-m-m @-OCII -C CH Ra s 0 c CHCHz0 R2 R2 0-cH=OH--om oHroHoHz a a N a Q a wherein A is a divalent radical selected from the group to about 6; carbon atoms, Cl, Br, -0--R wherein R consisting of alkylidene, cycloalkylidene, S IS an alkyl group having from 1 to about 6 carbon .S atoms, n has a value ofO or 1, X is O or S, and IS substituted tertiary amine or a substituted phosphine. o o 0 Disulfonamide salts such as represented by the above L' g l formulae l-IV include, for example, salts of diphenylet- 1L her-4-4-disulfonamide, di(bromophenyl)ether-4,4-

. disulfonamide, di(methylphenyl)ether-4,4- disulfonamide, di(butylphenyl)ether-4,4- h R2, R3 nd R4 are Independently alkyhdene disulfonamide, ether 44l groups and R7 and R8 are independently halo disulfonamide, di(chlorophenyl)ether-4,4- hydrogen or alkyl groups havmg from 1 to about disulfonamide, naphthalene-l,5-disulfonamide, methy- 4 carbon lnaphthalene-l,5-disulfonamide, ethyl-naphthalene- Suitable disulfonamide salts which are employed in Lidisultbnamide, dipropylnaphthalene l5 the latent l epoxy resm Composmons of the disulfonamide, chloronaphthalene-l ,S-disulfonamide, present invention include those represented by the genchlomnaphthalene 26 disulfonamide bromonaphthal eral formulae: ene-l ,S-disulfonamide, dibromonaphthalenel ,5-

disulfonamide, metaand para-phenylene disulfonamide, dibenzofuran disulfonamide, dibenzothiophene I. R R

i O 40 disulfonamide and the like, wherein the anionic moi- L Q (H eties (B) are substituted tertiary amines such as 2- ll IL methylimidazole, dimethyl aniline, triethylenediamine,

hexamethylene tetramine, triethylamine, triethanolo amine and the. like or hydrocarbon substituted tertiary I g phosphines such as triaryl phosphines such as triphenyl -NH -2B phosphine or trialkyl phosphines such as trimethyl 1L phosphine, triethyl phosphine and the like.

The disulfonamide starting materials are conve- 0 0 niently prepared by chlorosulfonating the desired aro- L matic compound with at least a stoichiometric quantity of a suitable chlorosulfonation agent such as, for exam- X ple, chlorosulfonic acid at a temperature of from about 0 longer. The resultant disulfonyl chloride after removal of any excess chlorosulfonation agent is then reacted with aqueous or anhydrous ammonia at 40-l50C. under autogenous pressure for from about 2 to about 24 hours. The resultant disulfonamide is then precipif 0 tated in cold water, filtered and the product is finally wherem A 15 a dwalem hydrocarbon group havmg mm recovered by slurrying the precipitate in hot water and 1 to about 6 Carbon atoms again filtering. The disulfonamide salts are those prepared from the disulfonamide by dissolving the disul- O 0 fonamide and the appropriate amount of base in a ketog! g nic solvent and then removing the solvent to obtain the A salt so produced.

The compositions of the present invention may also 50C. to reflux for from about 2 to about 6 hours or Coating solutions were prepared as in Table I from an epoxy resin (DER 331) employing-diphenyl oxide disulfonamide (DPODSA) as the latent curing agent and also containing salts of DPODSA with 2-methyl imidazole (2-Ml) or triphenyl phosphine (TPP). For comparative purposes, a coating solution was prepared employing 2-methyl imidazole alone as the curing agent. The coating compositions were applied to Bonderite 37 treated cold rolled steel panels at a coating thickness of about 0.5 mil., cured and tested as indicated in Table 11. Bonderite is the trade name of the Parker Rust 6 Proof Division of the Hooker Chemical Corporation for their phosphate surface coating for metals.

The Hot Tack Test is an indication of curing. A wooden tongue depressor wasv drawn across the hot coating surface and if the coating was marked, a lack of cure was indicated. If it was not marked, then the coating was deemed to have cured. in the Table, a yes indicates that the coating was marked by the tongue depressor while a no indicates that the coating was not marked.

The reverse impact test is carried out using a four pound dart having a one inch ball on its tip which is dropped from various heights onto the backside of the panel. Impact (weight of dart in pounds times the height of drop in inches) distorts the panel and coating into a cavity and indicates coating toughness. Pass means no fracture or flaking of the coating. Fail means the opposite.

MEK test is a solvent resistance spot test wherein a piece of paper toweling is saturated with methylethylketone, placed on the coating and covered with a watch glass for 3 minutes. The glass and towel are removed by wiping and the effect on the coating is observed.

TABLE I Coating Formulations Control Ex. 1 Ex. 2 Ex. 3 Ex. 4

DER 331* 69.8 g. 69.8 g. 69.8 g. 69.8 g. 69.8 g.

(0.367 eq.) DPODSA 30.2 g. 28.2 g. 26.2 g. 29.6 g. 28.55 g

(0.368 eq.) 2-Ml 1.2 g. l/1 2-M1- DPODSA Salt** 2.5 g. 5.0 g. 1/1 TPP DPODSA Salt 1.14 g. 2.96 g Dowanol EM*** 1000 g. 100.0 g. 100.0 g. 100.0 g. 100.0 g Catalyst (Based on Solids) 12 0.5 1.0 0.5 1.3

" Trademark diglycidyl ether of Bisphenol A having an epoxy equivalent weight of about 190 l/l Mole ratio mixtures of the compounds described and free DPODSA Trademark for the monomethyl ether of ethylene glycol TABLE ll Results of Oven Cures of Epoxy Coating Formulations Formulation Control Ex. 1 Ex. 2 Ex. 3 Ex. 4

350F. Cures 15 Minutes Hot Tack No No No 160 ln. Lb. Reverse lmpact Pass Pass Pass MEK Spot Test (3 Min.) -No effect -No effect -No effect 300F. Cures 15 Minutes Hot Tack No Yes Yes 160 1n. Lb. Reverse Impact Pass MEK Spot Test (3 Min.) Softens Minutes Hot Tack No Yes Yes 160 ln. Lb. Reverse Impact Pass MEK Test (3 Min.) No effect Minutes Hot.Tack No Yes No 160 ln. Lb. Reverse impact Pass Fails at about 20 ln. Lb. MEK Test (3 Min.) No effect Disintegrates (in./min.) Minutes Hot Tack No No No ln. Lb. Reverse lmpact Pass Fails, pass at Pass 80 ln. Lb. MEK Test (3 Min.) No effect Softens badly Slight at 1 Min. softening mulations are given in Table V Examples l-4 were stored at room temperature (25C.) in order to determine shelf lives. The results are shown in Table III.

A comparable control containing one equivalent of Table IV Latency of Dispersison Coating Sys dicyandiamide per equivalent of epoxy resin catalyzed h lf if months months with 0.5 percent Z-methyl imidazole by weight has a cam'yst i shelf life of 3-7 days. Example 1, after one month of 0.5% l agmg at room temperature, gave the same results when cast and cured as it had when freshly prepared indicat-- mg no loss in properties on aging.

TABLE III Latency of Solutions in Table I Example I 2 4 Shelf Life 2 months 2% weeks 6 months 3 months (Room Temp.) Catalyst Level 0.5% 1.0%, 0.5% l.3%

Z-Methyl 2-Methyl Triphenyl Triphenyl Imidazole Imidazole Phosphine Phosphine TABLE V Coating Formulations Example 7 9 10 ll DER 663* 95 g 95 g. 95 g. 95 g. 95 g. DPODSA 2.39 4.73 g. 6.28 g. 4.3 g. 6.0 g. DPODSA- 4/l** salt- 4/1 salt 3.5/I** salt- 6.5/l salt- 3.5/l** salt- Amine Salt 9.14 g. 6.80 g. 5.25 g. y 7.3 g. g. Amine 2-MI Dabco Triethanol Triethyl Amine Hexamethylene (triethylene Amine Tetramine diamine) 7: Amine Catalyst 0.5% 0.5% 0.5% 0.5% 0.5% Dowanol EM I70 g. I70 g. I70 g. 170 g. 170 g.

Trademark for the diglycidyl ether of Bisphenol A having an epoxy equivalent weight of about 775 Mole ratio of'DPODSA/amine in the salt mixture The above formualtions were applied to Bonderite 37 treated cold rolled steel panels at a coating thickness of about 0.5 mil and cured and tested as indicated in Examples 5 and 6 Examples 1 and 2 were repeated using 40 gms. of toluene in place of the 100 gms. of Dowanol EM. The

shelf lives of these examples are given in Table IV. Table VI.

A control using the same relative amounts of dicyan- TABLE VI Example 7 8 9 l0 11 Min. Time to Absence of 10 min. 10 min. min. 30 min. 10 min.

Hot Tack Reverse Impact Resistance at l in./lb. 160 in./lb. 160 in./lb. 160 in./lb. 160 in./lb.

Cure Cure Time to Resist Solvent Attack (1 min. 15 min. 10 min. 45 min. 30 min. 10 min. MEK4 Spot Test) diamide and 2-methyl imidazole as in the control for I clai the solution system above has a shelf life of about one 60 1, A l t t curing epoxy resin composition i week due to the solubility of the 2-methyl imidazole in i the resin-solvent mixture. I. an epoxy resin having an average of more than one 1,2-epoxy group per molecule,

2. an aromatic disulfonamide, and

3. a salt of an aromatic disulfonamide with substituted tertiary amines or hydrocarbon substituted phosphines selected from triaryl phosphines or tri- Examples 7-] I The procedures of Examples l-4 were repeated using DER 663 and various tertiary amines. The coating foralkyl phosphines wherein components l (2) and (3) are present in quantities so as to provide an amine hydrogen equivalentzepoxy equivalent ratio of at least about 09:1 and (3) is present in an amount greater than 1.0 weight percent based on the amount of (2).

2. The composition of claim 1 wherein the amine hydrogen equivalentzepoxide equivalent ratio is from about 0.911 to about 1.25:1 and the amount of aromatic disulfonamide salt used is in the range from 5.0 to 10 100.0 weight percent based on the aromatic disulfonamide.

3. The composition of claim 2 wherein the disulfonamide is diphenyl oxide disulfonamide.

4. The composition of claim 2 wherein the aromatic disulfonamide salt is a salt of an aromatic disulfonaresin is a glycidyl ether of bisphenol A with epichlorohydrin. v

7. The composition of claim 3 wherein the epoxy resin is a glycidyl ether of bisphenol A with epichlorohydrin.

8. A coating composition containing the composition of claim 1 and an organic solvent. 

2. The composition of claim 1 wherein the amine hydrogen equivalent:epoxide equivalent ratio is from about 0.9:1 to about 1.25:1 and the amount of aromatic disulfonamide salt used is in the range from 5.0 to 100.0 weight percent based on the aromatic disulfonamide.
 2. an aromatic disulfonamide, and
 3. a salt of an aromatic disulfonamide with substituted tertiary amines or hydrocarbon substituted phosphines selected from triaryl phosphines or trialkyl phosphines wherein components (1), (2) and (3) are present in quantities so as to provide an amine hydrogen equivalent:epoxy equivalent ratio of at least about 0.9:1 and (3) is present in an amount greater than 1.0 weight percent based on the amount of (2).
 3. The composition of claim 2 wherein the disulfonamide is diphenyl oxide disulfonamide.
 4. The composition of claim 2 wherein the aromatic disulfonamide salt is a salt of an aromatic disulfonamide with substituted tertiary amines or hydrocarbon substituted tertiary phosphines selected from triaryl phosphines or trialkyl phosphines.
 5. The composition of claim 4 wherein the substituted tertiary amine is 2-methyl imidazole, dimethyl aniline, triethylene diamine, hexamethylene tetramine, triethylamine or triethanolamine.
 6. The composition of claim 2 wherein the epoxy resin is a glycidyl ether of bisphenol A with epichlorohydrin.
 7. The composition of claim 3 wherein the epoxy resin is a glycidyl ether of bisphenol A with epichlorohydrin.
 8. A coating composition containing the composition of claim 1 and an organic solvent. 